1. Field of the Invention
This invention relates to a magnetic disk apparatus or magnetic disk drive provided with a mechanism which can protect a head and a disk from an impact when the apparatus drops or in a like case.
2. Description of the Related Art
In recent years, magnetic disk apparatus which are used as external storage apparatus for computers or like apparatus have increased recording density and reduced size and thickness. As the size and thickness of the magnetic disk apparatus is reduced, a portable magnetic disk apparatus has been developed which can be inserted into an IC card slot when it is to be used. When a portable magnetic disk apparatus is carried, it may possibly be acted upon by an impact as it dropped or the like. Since the acceleration by impact upon dropping amounts to several thousands G, a magnetic disk apparatus is required to have a high degree of reliability that, even when dropped, a head slider, a disk medium or any other element in the magnetic disk apparatus is not be damaged.
FIG. 10 is a perspective view, partly broken, of a conventional magnetic disk apparatus. The apparatus shown includes a pair of magnetic disk mediums 2, a spindle mechanism 4 for rotating the magnetic disk mediums 2, four head sliders 6 provided in an opposing relationship to the magnetic disk mediums 2 and each carrying thereon a magnetic head for writing and reading out information onto and from the opposing magnetic disk medium 2, a head suspension mechanism 8 for supporting each of the head slider 6, and an actuator 10 for actuating the head suspension mechanisms 8 to cause the magnetic heads to perform a seeking operation in a radial direction of the magnetic disk media 2.
The head suspension mechanism 8 includes a load beam and a gimbal. The actuator 10 includes an actuator arm assembly 16 mounted for rotation around a shaft 14 and having a plurality of (four) arms 17 on which the load beams of the head suspension mechanisms 8 are mounted, and a driving section (voice coil motor) 18 for driving the actuator arm assembly 16 to rotate.
Some of magnetic disk apparatus of the type just described include a loading/unloading mechanism (not shown). The loading/unloading mechanism extracts, when the power supply is disconnected, energy from inertial rotation of the spindle mechanism 4 as a back electromotive force of a spindle motor and flows an electric current through the voice coil motor of the actuator 10 to energize the actuator 10 so that the head suspension mechanisms 8 run on tapered run-on members provided on the cover or the like to lift the head sliders 6 from the magnetic disk media 2 to perform unloading. On the other hand, upon loading, the power supply is connected to energize the actuator 10 to move the head sliders 6 to stand-by tracks (also called zero cylinders) on the magnetic disk media 2.
Where the loading/unloading mechanism described above is employed, even if the head sliders are lifted and retracted upon unloading, when the head sliders are spaced away from the magnetic disk media or are loaded onto the magnetic disk media again, the head sliders move in an unstable manner, whereupon an edge of a head slider sometimes comes in contact with the opposing magnetic disk medium to causing a head crash.
Further, due to the fact that the rigidity of the head suspension mechanism or the loading/unloading mechanism is low, if an impact acts upon the apparatus due to its being dropped or the like, even after unloading has been performed, a head slider may collide with the magnetic disk medium to cause damage to the head slider or the magnetic disk medium. The loading/unloading mechanism provides further problems peculiar thereto such as the sufficiency of back electromotive force of the spindle motor, which is used as an energy source upon unloading, cannot be assured due to a drop in inertia of the rotating section and a drop in efficiency of the spindle motor as a result of reduction in size of the apparatus.